On-machine calibration method and system of star probe, medium and equipment

Abstract

The invention relates to the technical field of on-machine calibration compensation, and discloses an on-machine calibration method and system for a star probe, a medium and equipment, and the method comprises the steps: constructing a star probe model and a standard ball model, and generating a calibration measurement path according to the star probe model and the standard ball model, the calibration measurement path realizes calibration of the radius of the standard ball, the eccentricity of the measuring head, the equivalent radius of the measuring head and three-dimensional compensation values of the measuring head at different touch positions on the spherical surface of the standard ball; using a reference cutter to find the center position of the standard ball as the original point position of the calibration measurement path; on-machine measurement is carried out according to the calibration measurement path, and calibration of the star-shaped probe is achieved. According to the invention, three-dimensional high-precision calibration of the star probe can be realized, and the high-precision measurement requirement is met.

Description

Technical Field

[0001] The present invention relates to the technical field of on-machine calibration and compensation, and in particular to an on-machine calibration method, system, medium and equipment for a star-shaped stylus. Background Art

[0002] The stylus is an important component of the measurement system. When measuring a workpiece, the probe installed at the end of the stylus contacts the workpiece, causing the internal structure of the stylus to displace, thereby generating a relevant signal from the internal sensor. After receiving the relevant signal, the CNC machine tool obtains the current coordinate data of the stylus and workpiece. Based on this coordinate data, combined with the probe radius and the normal direction of the contact point, the accurate coordinate value of the workpiece is obtained.

[0003] In existing on-machine measurement, the commonly used stylus is a straight stylus, and the corresponding calibration is mostly 2D calibration, that is, only the length and radius of the straight stylus are calibrated. However, with the increasing number of application scenarios of CNC machining, the application of stylus in CNC machining is becoming more and more extensive, and the measurement requirements are also increasing. In addition to simple sub-division and medium-sized measurements, there are more and more scenarios for 3D coordinate measurement on inclined planes and curved surfaces, and the types of stylus have also expanded from straight stylus to more types, such as Figure 1 Star stylus shown.

[0004] When calculating workpiece coordinates, the accuracy of a star stylus's length, radius, and probe position and radius at any three-dimensional point on the stylus significantly impacts the calculation results. However, errors can occur during the actual production and assembly of star styli, leading to deviations in the stylus' length, diameter, probe position, and radius. After installation, the actual position and shape of the stylus may also deviate from the stylus model. Furthermore, when using a star stylus for measurement, styluses of varying lengths, shapes, and diameters must be selected based on the shape and size of the workpiece being measured. Wear can also cause radius deviations at different locations on the stylus's probe. Therefore, star styli calibration is necessary to ensure accurate measurement in various scenarios. When working with three-dimensional star styli, in addition to calibrating and compensating for length and radius, calibration and compensation must also be performed for other three-dimensional points on the star stylus. Otherwise, accurate measurement of tilted planes or 3D curved surfaces is impossible. Traditional 2D calibration methods are no longer effective for star styli calibration, hindering high-precision measurement requirements. Summary of the Invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide an on-machine calibration method, system, medium and equipment for a star-shaped stylus, which can realize three-dimensional high-precision calibration of the star-shaped stylus and meet high-precision measurement requirements.

[0006] To solve the above technical problems, the present invention provides an on-machine calibration method for a star-shaped stylus, comprising:

[0007] Constructing a star-shaped stylus model and a standard sphere model, and generating a calibration measurement path based on the star-shaped stylus model and the standard sphere model, wherein the calibration measurement path realizes calibration of the standard sphere radius, the stylus eccentricity, the stylus equivalent radius, and the three-dimensional compensation value of the stylus at different contact positions on the standard sphere surface;

[0008] Use the reference knife to find the center of the standard sphere as the origin of the calibration measurement path;

[0009] Perform on-machine measurement according to the calibrated measurement path to calibrate the star stylus.

[0010] Furthermore, the calibration method of the standard sphere radius is specifically as follows: finding the highest lateral point of the standard sphere, and obtaining the standard sphere radius according to the maximum diameter position of the standard sphere; updating the standard sphere radius by an iterative measurement method so that the standard sphere radius deviation is within a limited error range;

[0011] The calibrating method of the stylus eccentricity is specifically as follows: dividing the standard sphere into four points according to the radius of the standard sphere to find the stylus eccentricity; updating the stylus eccentricity by an iterative measurement method so that the stylus eccentricity deviation is within a limited error range.

[0012] Furthermore, the calibration method of the probe equivalent radius is specifically as follows:

[0013] The measuring points are set on the spherical surface of the standard sphere, and the fitting radius of the standard sphere is obtained by using the least squares method. Combined with the calibrated standard sphere radius, the equivalent radius of the probe is obtained: r1=Rr, where r1 is the equivalent radius of the probe, R is the fitting radius of the standard sphere, and r is the calibrated standard sphere radius.

[0014] Furthermore, the least squares method is used to perform spherical fitting to obtain the fitting radius of the standard sphere, specifically:

[0015] Obtain the measured point coordinate data of each measuring point, and construct the least squares fitting spherical equation based on the measured point coordinate data:

[0016] (xa)2+(yb)2+(zc)2=r2,

[0017] Among them, a, b, and c correspond to the three-dimensional coordinates of the center of the standard sphere;

[0018] The transformation least squares method is used to fit the spherical equation to obtain the formula expression:

[0019] -2xa-2yb-2zc+1*(a2+b2+c2-r2)=-x2-y2-z2,

[0020] Let d = a2 + b2 + c2 - r2, and the linear equations for the parameters a, b, c, and d are:

[0021] -2xa-2yb-2zc+d=-x2-y2-z2,

[0022] The three-dimensional coordinate data of each measuring point on the hemisphere of the measured standard sphere are recorded as (xi,yi,zi), i=1,…,n, where xi, yi, zi are the three-dimensional coordinate values of the i-th measuring point respectively, and n is the number of measuring points; according to the formula -2xa-2yb-2zc+d=-x2-y2-z2, n linear equations can be obtained, and the least squares method is used to solve the spherical equation fitted by the center point of the probe, thereby obtaining the fitting radius of the fitted standard sphere.

[0023] Furthermore, the calibration method of the three-dimensional compensation value of the probe at different contact positions on the spherical surface of the standard ball is specifically as follows:

[0024] Each time the probe contacts the standard sphere, the distance from the probe center to the standard sphere center is recorded as Li, where Li is the distance from the probe center to the standard sphere center when the probe contacts the standard sphere for the i-th time, i = 1,…,n, where n is the number of measurement points.

[0025] The deviation of the contact point on the probe is constructed as: Δri = Li-R-r1, where Δri is the deviation of the contact point on the probe when the probe contacts the standard ball for the i-th time, and Δri is used as the three-dimensional compensation value of the i-th contact position of the probe on the spherical surface of the standard ball.

[0026] Furthermore, the reference knife is used to find the center position of the standard ball as the origin position of the calibration measurement path, specifically:

[0027] Use the reference tool to touch the standard block, use the touch point as G54, and use the reference tool to find the center of the standard sphere as G55.

[0028] The present invention also provides an on-machine calibration system for a star-shaped stylus, comprising:

[0029] Model building module, used to build star stylus models and standard sphere models;

[0030] A calibration module is used to generate a calibration measurement path based on the star-shaped stylus model and the standard sphere model, wherein the calibration measurement path realizes the calibration of the standard sphere radius, the stylus eccentricity, the stylus equivalent radius, and the three-dimensional compensation value of the stylus at different contact positions on the standard sphere surface;

[0031] The coordinate origin establishment module is used to control the reference tool to find the center position of the standard sphere as the origin position of the calibration measurement path;

[0032] The execution module is used to control the machine to perform on-machine measurement according to the calibrated measurement path to achieve calibration of the star stylus.

[0033] Furthermore, the calibration module includes:

[0034] Reference point group module, used to measure the stylus length;

[0035] The pole group module is used to iteratively update the center position of the standard sphere;

[0036] Meridian group module, used to find the highest point of the standard sphere in the lateral direction and obtain the radius of the standard sphere;

[0037] The equatorial group module is used to center the standard sphere at four points according to its radius to obtain the eccentricity of the probe;

[0038] The spherical surface group module is used to set measurement points on the spherical surface of the standard sphere to obtain the equivalent radius of the probe and the three-dimensional compensation value of the probe at different contact positions on the spherical surface of the standard sphere.

[0039] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the on-machine calibration method of the star stylus is implemented.

[0040] The present invention also provides an on-machine calibration device for a star probe, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the on-machine calibration method for the star probe is implemented.

[0041] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0042] The present invention plans measurement points in a hemispherical area of the standard sphere surface to obtain the measured point coordinate data of each measurement point, and calibrates the star stylus based on these measured point coordinate data and the known standard sphere radius data. In addition to calibrating the length and radius of the stylus, the standard sphere radius, the eccentricity of the stylus, the equivalent radius of the stylus, and the three-dimensional compensation values of the stylus at different contact positions on the standard sphere surface are also calibrated, thereby realizing three-dimensional calibration of the star stylus, which can improve the measurement accuracy of the star stylus during use of the machine, and meet the high-precision detection requirements of products on CNC machine tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0044] Figure 1 This is an example diagram of a star-shaped stylus and a calibration sphere.

[0045] Figure 2 Flowchart of the method in the preferred embodiment of the present invention.

[0046] Figure 3 1 is a step diagram of a method in a preferred embodiment of the present invention.

[0047] Figure 4 This is an example diagram of a star-shaped stylus model constructed in a preferred embodiment of the present invention.

[0048] Figure 5 This is an example diagram of a standard sphere model constructed in a preferred embodiment of the present invention.

[0049] Figure 6 This is the calibration measurement path generated in the preferred embodiment of the present invention.

[0050] Figure 7 This is an example diagram of placing a standard ball on the machine table in a preferred embodiment of the present invention.

[0051] Figure 8 Schematic diagram of the radius and length of the stylus, and the radius and eccentricity of each stylus obtained in a preferred embodiment of the present invention.

[0052] Figure 9 This is an example diagram of using a reference knife to find points on a standard block in a preferred embodiment of the present invention.

[0053] Figure 10 3D compensation values of the probe at different contact positions on the surface of a standard sphere calibrated in a preferred embodiment of the present invention are exemplified in FIG. DETAILED DESCRIPTION

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0055] Reference Figure 2 、 Figure 3 As shown, the present invention discloses an on-machine calibration method for a star-shaped stylus, comprising the following steps:

[0056] S1: Constructing a star-shaped stylus model and a standard sphere model. In this embodiment, the star-shaped stylus model and the standard sphere model are constructed in the QJCAM software. The constructed star-shaped stylus model is as follows: Figure 4 As shown, the standard sphere model is Figure 5 As shown. QJCAM has a simple operating process, and 3D calibration in QJCAM ensures accuracy and stability. The machine tool in this example is a Hammer C12 five-axis machine, the probe is a Renishaw 400 probe with an R2 stylus, and the reference ball is a vertically mounted D25 stainless steel reference ball.

[0057] S2: Generate a calibration measurement path based on the star-shaped stylus model and the standard sphere model. The calibration measurement path generated in this embodiment is as follows: Figure 6 The calibration measurement path realizes the calibration of the length and radius of the stylus and the radius of the standard sphere, the eccentricity of the stylus, the equivalent radius of the stylus, and the three-dimensional compensation value of the stylus at different contact positions on the surface of the standard sphere.

[0058] S2-1: Use the common 2D calibration method to measure the length and radius of the stylus.

[0059] S2-2: Calibration method of the standard sphere radius, specifically: find the highest lateral point of the standard sphere, obtain the standard sphere radius according to the maximum diameter position of the standard sphere, and update the standard sphere radius through iterative measurement method to make the standard sphere radius deviation within the specified error range.

[0060] S2-3: The calibration method of the probe eccentricity is as follows: the standard sphere is divided into four points according to its radius, the probe eccentricity is found, and the probe eccentricity is updated by iterative measurement method so that the probe eccentricity deviation is within the specified error range.

[0061] S2-4: Calibration method of probe equivalent radius, specifically:

[0062] S2-4-1: Set measurement points on the hemisphere of the standard sphere (the number of measurement points is set according to actual conditions).

[0063] S2-4-2: Use the least squares method to perform spherical fitting to obtain the fitting radius of the standard sphere:

[0064] S2-4-2-1: Obtain the measured point coordinate data of each measuring point, and construct the least squares fitting spherical equation based on the measured point coordinate data:

[0065] (xa)2+(yb)2+(zc)2=r2,

[0066] Where a, b, and c correspond to the three-dimensional coordinates of the center of the standard sphere, and r>0;

[0067] S2-4-2-2: Transform the least squares method to fit the spherical equation to obtain the formula expression:

[0068] -2xa-2yb-2zc+1*(a2+b2+c2-r2)=-x2-y2-z2,

[0069] S2-4-2-3: Let d = a² + b² + c² - r², and the linear equations for the parameters a, b, c, and d are:

[0070] -2xa-2yb-2zc+d=-x2-y2-z2,

[0071] S2-4-2-4: The three-dimensional coordinate data of each measuring point on the hemisphere of the measured standard sphere are recorded as (xi,yi,zi), i=1,…,n, where xi, yi, zi are the three-dimensional coordinate values of the ith measuring point respectively, and n is the number of measuring points; according to the formula -2xa-2yb-2zc+d=-x2-y2-z2, n linear equations can be obtained, and the least squares method is used to solve the spherical equation fitted by the center point of the probe, so as to obtain the fitting radius of the fitted standard sphere, recorded as R, which is greater than the calibrated standard sphere radius r.

[0072] S2-4-3: Combined with the calibrated standard sphere radius, the equivalent probe radius is obtained as: r1 = Rr, where r1 is the equivalent probe radius, R is the fitted radius of the standard sphere, and r is the calibrated standard sphere radius. In this embodiment, the equivalent probe radius is also updated through iterative measurement to ensure that the deviation of the equivalent probe radius is within a specified error range.

[0073] S2-5: The calibration method of the three-dimensional compensation value of the probe at different contact positions on the surface of the standard sphere is as follows:

[0074] At each measuring point on the hemisphere of the standard sphere, when the probe contacts the standard sphere, there is a distance between the center of the probe and the center of the standard sphere, which is recorded as Li. Li is the distance between the center of the probe and the center of the standard sphere when the probe contacts the standard sphere for the i-th time, i = 1,…,n, and n is the number of measuring points.

[0075] The deviation of the contact point on the probe is constructed as: Δri = Li-R-r1, where Δri is the deviation of the contact point on the probe when the probe contacts the standard sphere for the i-th time, r1 is the calibrated equivalent radius of the probe, and R is the fitting radius of the standard sphere. Based on this, Δr1, Δr2...Δrn can be obtained; Δri is used as the three-dimensional compensation value of the i-th contact position of the probe on the spherical surface of the standard sphere.

[0076] If, during the uncalibrated measurement process, the measurement point does not belong to the measurement point set during calibration, compensation is achieved based on the smooth transition between the measurement points set during calibration.

[0077] S3: If Figure 7 As shown, place the standard ball on the machine table, and use the reference knife to find the center position of the standard ball as the origin position of the calibration measurement path.

[0078] like Figure 9 As shown, use the reference tool to touch the standard block, use the touch point as G54, and use the reference tool to find the center of the standard sphere as G55.

[0079] In this embodiment, when searching for the center position of the standard ball, the center position of the quasi-ball is updated by an iterative measurement method so that the deviation of the center position of the standard ball is within a limited error range.

[0080] S4: Perform on-machine measurement according to the calibrated measurement path to calibrate the stylus length, radius and reference sphere radius, probe eccentricity, probe equivalent radius, and three-dimensional compensation values at different contact positions of the probe on the reference sphere surface, thereby achieving calibration of the star stylus. Figure 8 This is an example diagram of the radius (shown as diameter) and length of the calibrated stylus in this embodiment, and the radius (shown as diameter) and eccentricity of each stylus (i.e., stylus tip). Figure 10 3D compensation values of the probe at different contact positions on the surface of the standard sphere calibrated in this embodiment are exemplified in FIG.

[0081] The invention also discloses an on-machine calibration system for a star-shaped stylus, comprising a model building module, a calibration module, a coordinate origin establishment module and an execution module.

[0082] Model building module, used to build star stylus models and standard sphere models.

[0083] The calibration module is used to generate a calibration measurement path based on the star-shaped stylus model and the standard sphere model. The calibration measurement path realizes the calibration of the standard sphere radius, the stylus eccentricity, the stylus equivalent radius, and the three-dimensional compensation value of the stylus at different contact positions on the spherical surface of the standard sphere.

[0084] The calibration module includes: a reference point group module for measuring stylus length; a pole group module for iteratively updating the center position of the calibration sphere; a meridian group module for finding the highest lateral point of the calibration sphere to obtain the calibration sphere radius; an equatorial group module for performing four-point centering and eccentricity calibration based on the calibration sphere radius; an equatorial group module for centering the calibration sphere at four points based on the calibration sphere radius to obtain the probe eccentricity; and a spherical group module for setting measurement points on the surface of the calibration sphere. The measurement points vary depending on the stylus type, and the distribution area and range can be set using parameters. This yields the probe's equivalent radius and three-dimensional compensation values for different contact positions on the calibration sphere surface.

[0085] The coordinate origin establishment module is used to control the reference tool to find the center position of the standard sphere as the origin position of the calibration measurement path.

[0086] The execution module controls the machine to perform on-machine measurements according to the calibration measurement path, thereby calibrating the star stylus. In this embodiment, the execution module generates a calibration measurement program based on the calibration measurement path and sends it to the CNC system, which automatically executes it. After the calibration measurement program is executed, the measurement results are transmitted back to the QJCAM software, which uses this data to perform three-dimensional compensation on the star stylus. This entire process enables automated iterative measurement, ensuring the accuracy of the calibration results.

[0087] On the machine side, the following operations are performed: Using a reference tool to touch the reference block, the current contact point is set as the origin (G54). Using the reference tool to locate the center of the reference sphere, the new center coordinates are assigned to G55. Off-machine tool setting is performed using a star stylus, and the tool length is entered into the tool table.

[0088] The present invention also discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, an on-machine calibration method for a star probe is implemented.

[0089] The present invention also discloses an on-machine calibration device for a star probe, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, an on-machine calibration method for a star probe is implemented.

[0090] The present invention plans measurement points in a hemispherical area of the standard sphere surface to obtain the measured point coordinate data of each measurement point, and calibrates the star stylus based on these measured point coordinate data and the known standard sphere radius data. In addition to calibrating the length and radius of the stylus, the standard sphere radius, the eccentricity of the stylus, the equivalent radius of the stylus, and the three-dimensional compensation values of the stylus at different contact positions on the standard sphere surface are also calibrated, thereby realizing three-dimensional calibration of the star stylus, which can improve the measurement accuracy of the star stylus during use of the machine, and meet the high-precision detection requirements of products on CNC machine tools.

[0091] This invention combines on-machine measurement with precision gauges like standard spheres to mitigate errors introduced by stylus production, assembly, and installation, thereby accurately determining the three-dimensional position of the star-shaped stylus probe's center, its actual radius, and the three-dimensional compensation values for each point on the probe. This not only expands the selection of stylus types for on-machine measurement, broadening its application scope, but also improves the accuracy of on-machine inspection, particularly in precision machining, ensuring a high product yield before it leaves the machine, thereby reducing the rework rate and shortening the production cycle.

[0092] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0093] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0094] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0095] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0096] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for on-machine calibration of a star-shaped stylus, characterized in that: include: Constructing a star-shaped stylus model and a standard sphere model, and generating a calibration measurement path based on the star-shaped stylus model and the standard sphere model, wherein the calibration measurement path realizes calibration of the standard sphere radius, the stylus eccentricity, the stylus equivalent radius, and the three-dimensional compensation value of the stylus at different contact positions on the standard sphere surface; Use the reference knife to find the center of the standard sphere as the origin of the calibration measurement path; Perform on-machine measurement according to the calibrated measurement path to calibrate the star stylus.

2. The on-machine calibration method for a star stylus according to claim 1, characterized in that: The calibration method of the standard sphere radius is specifically as follows: finding the highest lateral point of the standard sphere and obtaining the standard sphere radius according to the maximum diameter position of the standard sphere; updating the standard sphere radius by an iterative measurement method so that the standard sphere radius deviation is within a limited error range; The calibrating method of the stylus eccentricity is specifically as follows: dividing the standard sphere into four points according to the radius of the standard sphere to find the stylus eccentricity; updating the stylus eccentricity by an iterative measurement method so that the stylus eccentricity deviation is within a limited error range.

3. The on-machine calibration method for a star stylus according to claim 1, characterized in that: The calibration method of the probe equivalent radius is specifically as follows: The measuring points are set on the spherical surface of the standard sphere, and the fitting radius of the standard sphere is obtained by using the least squares method. Combined with the calibrated standard sphere radius, the equivalent radius of the probe is obtained: r1=Rr, where r1 is the equivalent radius of the probe, R is the fitting radius of the standard sphere, and r is the calibrated standard sphere radius.

4. The on-machine calibration method for a star stylus according to claim 3, characterized in that: The least squares method is used to perform spherical fitting to obtain the fitting radius of the standard sphere, specifically: Obtain the measured point coordinate data of each measuring point, and construct the least squares fitting spherical equation based on the measured point coordinate data: (xa)2+(yb)2+(zc)2=r2, Among them, a, b, and c correspond to the three-dimensional coordinates of the center of the standard sphere; The transformation least squares method is used to fit the spherical equation to obtain the formula expression: -2xa-2yb-2zc+1*(a2+b2+c2-r2)=-x2-y2-z2, Let d = a2 + b2 + c2 - r2, and the linear equations for the parameters a, b, c, and d are: -2xa-2yb-2zc+d=-x2-y2-z2, The three-dimensional coordinate data of each measuring point on the hemisphere of the measured standard sphere are recorded as (xi,yi,zi), i=1,…,n, where xi, yi, zi are the three-dimensional coordinate values of the i-th measuring point respectively, and n is the number of measuring points; according to the formula -2xa-2yb-2zc+d=-x2-y2-z2, n linear equations can be obtained, and the least squares method is used to solve the spherical equation fitted by the center point of the probe, thereby obtaining the fitting radius of the fitted standard sphere.

5. The on-machine calibration method for a star stylus according to claim 3, characterized in that: The calibration method of the three-dimensional compensation value of the probe at different contact positions on the spherical surface of the standard ball is specifically as follows: Each time the probe contacts the standard sphere, the distance from the probe center to the standard sphere center is recorded as Li, where Li is the distance from the probe center to the standard sphere center when the probe contacts the standard sphere for the i-th time, i = 1,…,n, where n is the number of measurement points. The deviation of the contact point on the probe is constructed as: Δri = Li-R-r1, where Δri is the deviation of the contact point on the probe when the probe contacts the standard ball for the i-th time, and Δri is used as the three-dimensional compensation value of the i-th contact position of the probe on the spherical surface of the standard ball.

6. The on-machine calibration method for a star stylus according to any one of claims 1 to 5, characterized in that: The reference knife is used to find the center position of the standard ball as the origin position of the calibration measurement path, specifically: Use the reference tool to touch the standard block, use the touch point as G54, and use the reference tool to find the center of the standard sphere as G55.

7. An on-machine calibration system for a star-shaped stylus, characterized in that: include: Model building module, used to build star stylus models and standard sphere models; A calibration module is used to generate a calibration measurement path based on the star-shaped stylus model and the standard sphere model, wherein the calibration measurement path realizes the calibration of the standard sphere radius, the stylus eccentricity, the stylus equivalent radius, and the three-dimensional compensation value of the stylus at different contact positions on the standard sphere surface; The coordinate origin establishment module is used to control the reference tool to find the center position of the standard sphere as the origin position of the calibration measurement path; The execution module is used to control the machine to perform on-machine measurement according to the calibrated measurement path to achieve calibration of the star stylus.

8. The on-machine calibration system for a star stylus according to claim 7, characterized in that: The calibration module includes: Reference point group module, used to measure the stylus length; The pole group module is used to iteratively update the center position of the standard sphere; Meridian group module, used to find the highest point of the standard sphere in the lateral direction and obtain the radius of the standard sphere; The equatorial group module is used to center the standard sphere at four points according to its radius to obtain the eccentricity of the probe; The spherical surface group module is used to set measurement points on the spherical surface of the standard sphere to obtain the equivalent radius of the probe and the three-dimensional compensation value of the probe at different contact positions on the spherical surface of the standard sphere.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the on-machine calibration method for a star stylus according to any one of claims 1 to 6 is implemented.

10. An on-machine calibration device for a star-shaped stylus, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the on-machine calibration method for a star stylus according to any one of claims 1 to 6 is implemented.

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